'It's really dirty in there,' warned our cave guide as we made our way to the disused Box Freestone Mine, near Chippenham, where Blacksand were launching their debut album, Barn. 'And there is some crawling involved.' We picked our way over boulders, past roosting bats and through the labyrinthine corridors to the Cathedral, a massive man-made mining cavern.

Blacksand - Nick Franglen and Charles Casey - were keen to find out how their improvised music would work in this vast space. With water dripping around them, the dimly lit duo produced their vivid soundscapes until the power - running off a car battery - threatened to give out.

Blacksand are basically a guitar duo, feeding their instruments through a mass of effects pedals and units. Listening to Barn, this is far from obvious. When the music is at its most abstract, the ear picks out ghosts of other instruments that aren't there.

Some luminous acoustic picking ushers in the lengthy opener, 'Probe One'; then it feels like a door has suddenly shut, leaving the listener surrounded by slow-moving currents of sound. Twangy motifs reminiscent of Angelo Badalamenti soon emerge from the fog; multi-layered loops that sound like they are emanating through ancient rock.

Where will Blacksand take us next? The pair have a plan: to play in a Russian submarine in Kent's River Medway.